Sthil FS80

calm1(6)July 29, 2013

Hello,
Sthil FS80, starts perfect, idles fine, runs wide open great for about 5 mims. then no power. Plug gap is perfect, the ceracic is a light brown, tan color, spark screen is clean. Running 50:1 gas. At the time it starts losing power I believe it is getting hotter than usual. I use to be able to run this thing for 3-4 hours wide open with no problem. Any suggestions please let me know.
Thanks
Ed

Ed: From what you describe as losing power is rather vague , If there is a miss along with power loss then the ignition module could be suspect . This is common once the unit is warmed up . Otherwise you may well have a little lean fuel condition which would show the same symtoms , overheating and sudden loss of power. The cause could be loose or cracked fuel lines either external or internal at the entry point of the fuel tank along with a partially restricted fuel filter .The ceramic or electrode tan colour is marginal determination of correct fuel / air mixture. Light brown to brown is normal any lighter and your within the lean condition. Once all lines and carb flange tightness has been inspected you may try adjusting the carb a little richer . If these do not Help than you may have to try the module route .

Ewalk,
Forgot I posted on here! Checked the fuel lines & filter they
were fine. Took the carb apart & blasted it with carb cleaner,
put everything back together. Pushed the primer 10 times put the choke on pulled the cord, & she started perfect, moved the choke to run & let it set 30 seconds. Now it is a screaming machine. The one thing that I thought was kind of strange was the carb has no "high" adjustment. I did find a screw that lifts a cam that the throttle cable rides on. I raised that cam to the point that the tab of the "throttle tang" would hit the solid stop & therefore actually run wide open.
Thinking running less than wide open could be a big cause of the over heating issue. Now she screams!!
Thanks
Ed